Determination Of Singlet Oxygen Quantum Yield Of A Porphyrinic Metal-Organic Framework

Metal-organic frameworks (MOFs) have emerged as heterogeneous photosensitizers in applications ranging from photodynamic therapy to photocatalysis. However, singlet oxygen (O-1(2)) quantum yields of MOF photosensitizers are largely unknown. Herein, we report a reliable method to quantify the O-1(2) quantum yield of a porphyrin MOF PCN-222/MOF-545 (free base). To accurately measure the optical density of the MOF suspensions in chloroform, a UV-vis spectrometer equipped with an integrating sphere detector was employed. However, no O-1(2) near-infrared luminescence signal from the excited MOF could be detected and the amount of O-1(2) produced by the MOF photosensitizer was quantified using a O-1(2) trap 9,10-dimethylanthracene. Using C-70 as a reference, the O-1(2) quantum yield of PCN-222/MOF-545 (free base) was determined to be 0.35 +/- 0.02. This method should be applicable to the determination of O-1(2) quantum yields of other solid-state materials.